This invention relates to measuring devices and, more particularly, to a system for determining and transmitting the position of a movable element with respect to a reference.
There are many applications for systems which accurately measure the position of an element or workpiece from a reference point. In the case of three-dimensional space, the location of the point is determined by its X, Y and Z positions. To acquire the location of the point in the three-dimensional space, each of the X, Y and Z axes may be provided with devices for determining the X, Y and Z distances of the point from the zero reference point. Often rotary resolvers are coupled to a screw and slide assembly where the number of rotations of the screw determine the linear position of the slide from the reference point. Similarly, a rotary resolver may be coupled to a rotatable shaft on which is mounted a drum. As a flexible member is removed from the drum, the drum rotates and the length of the flexible member removed from it is proportional to the angular position of the shaft. There are a number of systems which measure the particular location of a point with respect to a reference coordinate system, many of which employ resolvers. However, many of these systems are not capable of providing accurate measurement of the displacement from a fixed reference. They do not provide for translating the absolute angular position of a shaft into units of distance. Some are expensive and if more than one axis is to be measured, there is a significant duplication of parts.
We have invented a system which can accurately measure the distance of a point from a reference wherein the point is acquired by determining the angular positon of a shaft and accurately converting the angular position into linear information. The system is capable of measuring many position axes and can process position information of a plurality of channels, each channel representing a position or distance along an axis. Duplication of various components within the system is minimized by employing multiplexing techniques.